1. Field of the Invention
This invention relates to screw presses.
2. Prior Art
Known screw presses comprise a press frame, a slide which is vertically movable in the press frame and supports the upper die, a threaded spindle operative between the press frame and the slide, a driven disc flywheel and a clutch disc which is connected rotationally rigidly to the spindle and can be connected by friction contact to the flywheel for the operating stroke of the slide, and piston-cylinder units acting between the press frame and the slide for returning the slide to the starting position.
In this connexion the spindle can be supported in an axial bearing in the upper crossbar of the press frame, the threaded shaft of the spindle engaging in a threaded nut in the slide. It is also possible, however, for a threaded nut, into which the threaded shaft of the spindle engages, to be inserted into the upper crossbar of the press shaft, a thrust bearing then being provided between the lower end of the spindle and the slide.
At each operating stroke of screw presses of this type the continuously driven flywheel is connected to the clutch disc by actuation of a friction clutch, as a result of which the spindle connected rotationally rigidly to the clutch disc is rotated. As the spindle rotates, the slide--depending upon its design--is pushed down by the threaded shaft by way of the threaded nut inserted therein or by the descending spindle by way of a thrust bearing in the slide. Depending upon the forging requirements the friction clutch is lifted again as a function of its force or its path. The slide is then moved back into the starting position by the piston-cylinder units which are operative between the press frame and the slide and which are acted upon hydraulically or pneumatically, and the spindle provided with a lead above the automatic lock rotates back.
Both during the execution of the forging blow and during the return movement of the slide with returning rotation of the spindle derived therefrom, the flanks which are always the same bear against one another in the threaded nut and on the threaded shaft and in the multiple-collar thrust bearing and on the collar pin or in the thrust bearing, as a result of which difficulties arise during lubrication. In order to eliminate such difficulties, correspondingly expensive lubricating apparatus and arrangements are required to supply lubricant under high pressure to all the sliding surfaces.
It would therefore be desirable to be able to ensure reliable lubrication with simple means.